Summer is the season for harmful algae blooms in many U.S. lakes and bays. They occur when water bodies become overloaded with nitrogen and phosphorus from farms, water treatment plants and other sources. Warm water and lots of nutrients promote rapid growth of algae that can be toxic and potentially fatal to aquatic life and people.

Eventually algae settle to the bottom and decay, depleting dissolved oxygen in the water, creating hypoxia – “dead zones” where oxygen levels are low enough to kill fish.

As a senior scientist at the National Oceanographic and Atmospheric Administration between 1975 and 2003, I developed annual hypoxia forecasts for the Chesapeake Bay and the Gulf of Mexico – two of our nation’s water bodies most harmed by these blooms. At the University of Michigan, I helped develop harmful algae bloom forecasts for Lake Erie and continue to work with public and private organizations on these issues.

University of Michigan professor Donald Scavia discusses the 2015 forecasts.

States around Lake Erie and in the Mississippi River basin, which drains to the Gulf of Mexico, have been trying to reduce nutrient pollution for years. They rely primarily on voluntary steps, such as offering grants to farmers to take steps to prevent fertilizer from washing off their fields.

In contrast, states around the Chesapeake have had more success with a federally enforced plan that can impose mandatory actions across the bay’s 64,000-square-mile watershed. From my perspective, when we compare these two approaches it is clear that voluntary measures are not even making modest dents in nutrient pollution.

The Chesapeake Bay watershed covers more than 64,000 square miles in parts of six states and the District of Columbia.Kmusser, CC BY-SA

The Chesapeake forecast predicts a 1.9-cubic-mile hypoxic region – nearly the volume of 3.2 million Olympic-size swimming pools. This is much larger than goals reflected in recent policies.

Nonetheless, at least the Chesapeake is moving in the right direction. The amount of nutrients flowing into the bay is starting to decline.

The long quest to clean up Lake Erie

Lake Erie first suffered from heavy nutrient pollution in the 1960s. The Clean Water Act of 1972 triggered a remarkable cleanup. Nutrients, primarily from point (discreet) sources like sewage treatment plants, were cut in half, and the lake responded quickly.

But harmful algae blooms and hypoxia resurfaced in the mid-1990s, probably because flows into the lake of a form of phosphorus that is readily used by algae tripled. The dead zone set a new record in 2012, and harmful algae blooms set records in 2011 and 2015. Even if blooms do not become toxic, they can have devastating effects. For example, the 2011 harmful algae blooms on Lake Erie cost the region nearly US$71 million in diminished property values, water treatment, and lost tourism revenues and recreational opportunities.

In response, the United States and Canada negotiated new phosphorus loading targets that call for a 40 percent reduction from 2008 levels. Ontario, Ohio, Michigan, Indiana, Pennsylvania and New York are developing domestic action plans to meet those targets.

Now however, 71 percent of nutrients entering Lake Erie are from non-point sources – mainly from agriculture. Non-point source pollution comes from diffuse sources, such as fertilizer washing off of farms and lawns, so it is harder to control.

The United States contributes over 80 percent of Lake Erie’s total phosphorus load. In sum, major load reductions will have to come from agriculture, mostly from U.S. farms.

How effective are voluntary measures?

Governments generally are averse to imposing environmental regulations on farmland. As a result, most action plans for Lake Erie rely on voluntary, incentive-based programs to address nutrient loss from agricultural lands.

The Chesapeake Bay’s pollution diet

States around the Chesapeake Bay also struggled for decades to make voluntary, incentive-based approaches work. Their efforts were overwhelmed by the impacts of population growth and agricultural production.

Frustrated by worsening conditions, the states asked EPA in 2010 to establish a total maximum daily load – a “pollution diet” within a regulatory framework under the Clean Water Act that limits the amount of nutrients and sediment that can enter the bay. Bay states and the District of Columbia then developed implementation plans and management strategies detailing how and when each jurisdiction would meet its individual goals.

Unlike voluntary strategies, this approach has teeth. If states miss interim milestones for reducing pollutants, EPA can impose “backstop measures,” such as requiring additional reductions from point sources and withholding federal grant money.

As I have detailed before, taming nutrient pollution will require a broad national approach that includes steps such as modifying the American diet, changing agricultural supply chains and reducing production of corn-based ethanol. We also need to find the will to set legally binding limits when voluntary steps aren’t enough.

Detail from a satellite photo of Lake Okeechobee’s algae bloom and the St. Lucie canal into which water was released. Rising water levels from heavy winter rains had water managers worried that water would breach the dike.
NASA